Fuels based on biocomponent sources will become increasingly prevalent in the future. Already, various governments have instituted current and future requirements that motor fuel pools contain a minimum percentage of fuel derived from a biocomponent source, such as a plant, animal, fish, or algae based oil or fat.
Producing diesel fuel from biocomponent sources presents a variety of challenges. In particular, for diesel hydroprocessing units that operate at low pressures, the presence of the additional heteroatoms in a biocomponent based diesel feed may pose difficulties. Modifying and/or replacing low pressure units to allow for higher processing pressures would require expensive capital investment.
What is needed is a method to allow for hydroprocessing of diesel feeds that are at least partially based on a biocomponent source without requiring significant new construction at refineries. The method should allow for production of an ultra low sulfur diesel product.
EP1693432 describes co-processing of vegetable oils with various diesel type mineral refinery feeds. The method appears to include combining a vegetable and mineral oil, hydrotreating the combined oil, and stripping off gas phase products.
US Published Patent Application 2008/0161614 describes two stage co-processing of a feed including both vegetable/animal and mineral oil. The first stage is operated at lower severity to primarily treat the vegetable and/or animal oil in the feed. The product of the first stage is then stripped to remove gas phase impurities. The stripped product is then hydrotreated in a more severe hydrotreatment stage to produce a diesel fuel.